Common Alderfly (Sialis lutaria), 13 May 2019. New Garden record. Photo Alan Crawford.

On 13 May 2019, Alan Crawford, one of the wildlife photographers that regularly visit the Garden, photographed an unusual insect and identified it as being an alderfly. There are three alderfly species native to the British Isles and all of them occur in Scotland. Alan’s photograph has been identified as Common Alderfly (Sialis lutaria, family Sialidae) on the basis of wing venation features. The addition of this wildlife record takes the Garden’s total to the end of May 2019 up to 1,092 species.

Alderflies constitute the order Megaloptera, an insect group not previously recorded in the Garden. They are rather primitive insects whose nearest relatives are the lacewings (order Neuroptera). All of them have aquatic larvae that live in ponds and rivers. The adults, like mayflies (order Ephemeroptera), have very short lifespans of only three or four days, during which they do not eat anything; instead they devote their short lives to finding a mate and laying eggs to start the reproductive cycle all over again. Alan was therefore very fortunate to find and photograph this fragile insect before its brief adult life came to an end.